This invention relates to hand pumps for dispensing liquid or paste substances contained in bottles.
Hand pumps of this type are well known and have been used for many years. They consist substantially of an elongated hollow body open at its two ends and composed of various cylindrical or slightly frusto-conical portions, which are mutually coaxial. A coaxial ring member is fixed to this body, normally by snap-fitting, to enable the pump to be fixed coaxially, either by snap-fitting or by screwing, to the mouth of the respective bottle containing the substance to be dispensed.
At one of the two end apertures of the hollow body there is provided a non-return valve, called hereinafter the inlet valve, which opens to enable a predetermined quantity of the substance contained in the bottle to be drawn in and fill an intake chamber provided in the hollow body in communication with said valve. Intake is via a tube fixed to the lower end of the hollow body and dipping into the substance contained in the bottle.
From the other aperture of the hollow body there upwardly projects a hollow coaxial stem open at its two ends. This stem can move axially in both directions within the hollow body and is secured in various ways to a coaxial piston which can also slide in both directions under sealed conditions within the hollow body.
This intake chamber is in communication with the inner channel of the hollow stem, which is itself in communication with the interior, but this communication is interrupted during the intake stage by a second non-return valve, called hereinafter the outlet valve, which closes during draw-in i.e. during filling of the intake chamber) and opens during the dispensing stage i.e. during emptying of the intake chamber).
The pump is operated by completely pressing the stem vertically inwards axially by a dispenser knob fixed to that end of the stem which projects outwardly.
The dispenser knob also normally comprises an outlet channel or spout for the substance to be dispensed, this channel being in communication with the channel in the stem.
On releasing the dispenser knob a certain vacuum is generated within the intake chamber, thus opening said inlet valve so that this chamber fills with a certain quantity of the substance contained in the bottle, drawn in through said dip tube. When the intake chamber has been filled, the inlet valve closes. A certain quantity of air, which enters the bottle through suitable holes provided in the pump hollow body, takes the place of the quantity of substance withdrawn from the bottle.
If the dispenser knob is again pressed completely down, said inlet valve remains closed whereas the outlet valve opens under the action of the piston which compresses the substance contained in the intake chamber, to allow the quantity of substance contained in the intake chamber to be dispensed. Releasing the dispenser knob results in a return to the described starting conditions, and the cycle can then be repeated.
A first drawback of the described pumps is that there is nothing to prevent the dispenser knob being accidentally pressed, for example when the bottle is carried in a handbag. This drawback is obviated by providing a normal removable cover (see U.S. Pat. No. 2,956,509 FIGS. 1 and 5, and U.S. Pat. No. 3,414,169 FIG. 4) which protects the dispenser knob against erroneous pump operation. A further method is to provide a locking device for the dispenser knob. This is normally a screw-locking device (see GB-B-No. 1,171,947 FIG. 2, GB-B-No. 910,791 FIGS. 1-5, and U.S. Pat. No. 3,228,347 FIGS. 1 and 2) or a snap device (see GB-B-No. 1,174,015 FIG. 1 and EP-A-No. 65214 FIGS. 1 and 2). The locking device of the snap type is operated by pressing the dispenser knob down beyond the end of its operating stroke with a force greater than that for normal dispensing.
Commercially available bottles are often provided neither with the protection cover nor with one of the aforementioned said types of locking device.
Pumps provided with a locking device for the dispenser knob suffer also from a further problem. In this respect, it can happen that the bottle, which is normally made of plastic material, is subjected to external pressure which can be considerable and cause the non-return valve to open. This produces undesirable leakage of the bottle contents. This situation can for example arise during storage or transport.
GB-No. 1,171,947 describes a hand pump which does not suffer from this drawback. It is however extremely complex, of very complicated construction and assembly and therefore costly. To obtain a seal in this situation, this pump is provided with three seal positions (see FIG. 2 of said patent). A first seal is achieved between the conical surface 24 and the relative inlet port 20 (which together form the inlet valve 23). A second seal is achieved between the cylindrical surface 65 and the lower portion of the cylindrical surface 64, and a third seal between the conical surface 60a and the lower mouth 61 of the sleeve 62.
It should also be noted that the seal surfaces 23, 65 and 60 are all provided on the element 58, which is in one piece with the closure element 24 of the inlet valve 23. For this reason the response of the valve 23 when a vacuum is produced in the chamber 30 relatively slowly and its opening occurs with a certain delay.